This invention relates to a wiring substrate comprising a wiring substrate with a wiring pattern formed thereon, a gas discharge display device using the same , and a method therefor.
Gas discharge display devices such as plasma display and the like make display through a self-luminescence, and therefore are characterized in that the field angle is large, the display is easy to see, the thickness can be lessened, and a large picture plane can be realized. Thus, such gas discharge display devices have become applied to display devices of information terminal equipment and high-quality picture tubes of television. Plasma displays are roughly classified into direct current driving type and alternate current driving type. Among them, the alternate current type of plasma display shows a high luminance owing to the memory action of dielectric layer covering electrodes, and its lifetime has reached a practical level through formation of protective layer. This results in practical application of plasma displays to video monitors for many uses.
FIG. 9 is a perspective view illustrating the structure of a practical plasma display panel, wherein the front side substrate 100 is shown apart from the back side substrate 200 for the purpose of facilitating understanding.
The front side substrate 100 comprises a display electrode 600 made of a transparent conductive material such as ITO (indium tin oxide), tin oxide (SnO.sub.2) or the like, a bus electrode 700 made of a low-resistance material, a dielectric layer 800 made of a transparent insulating material and a protecting layer 900 made of magnesium oxide (MgO) or the like, all being formed on a front side glass substrate 400.
The back side substrate 200 comprises an address electrode 1000, a barrier rib 1100 and a fluorescent material layer 1200, all formed on a back side glass substrate 500. Although not shown in FIG. 9, a dielectric layer 1300 is formed on the address electrode 1000, too.
By affixing the front side substrate 100 to the back side substrate 200 so that the display electrode 600 makes an approximately right angle with the address electrode 1000, a discharge space region 300 is formed between the front side substrate 100 and the back glass side substrate 500.
In this gas discharge display device, an alternate current voltage is applied between one pair of display electrodes 600 provided on the front side substrate 100, and a voltage is applied between the address electrode 1000 provided on the back side substrate 200 and the display electrode 600, whereby an address discharge is made to occur and a main discharge is generated in a prescribed discharging cell. The main discharge generates an ultraviolet ray, which induces emission of lights from the red- green- and blue-color fluorescent materials 1200 separately coated on respective discharging cells. A display is made by emission of these lights.
Examples of such prior gas discharge display devices are described in, for instance, FLAT PANEL DISPLAY 1996 (Edited by Nikkei Microdevice, 1995), pages 208-215.
Here, the method for forming the bus electrode 700 carried on the front side substrate 100 and the address electrode 1000 carried on the back side substrate 200 will be mentioned below in more detail. FIG. 5, 8A-8O illustrate an exemplary process for forming address electrode 1000 on back side glass substrate 500. Explanation of the process for forming bus electrode 700 carried on front side substrate 100 is omitted, because it can be formed by a similar process.
First, a Cr/Cu/Cr layer (1000a-c) for forming address electrode 1000 on the back side glass substrate 500 and a resist 2500 for forming the pattern of address electrode 1000 are successively piled lamination-wise by a film-forming technique such as sputtering, evaporation, spin coating, dry filling, etc. (Step (a), FIG. 8A: Film forming step). Next, the resist 2500 is exposed to light and developed so as to form a desired pattern of address electrode 1000 (Steps (b) and (c), FIGS. 8B and 8C: Photolithographic step). Next, using an etching solution for Cr, the Cr layer 1000a is etched to form the desired pattern (Step (d), FIG. 8D: Etching step). Next, the exposed and developed resist 2500 is peeled off, and a resist 2500 is again formed (Steps (e) and (f), FIGS. 8E and 8F). The above-mentioned treatments are repeated for each of Cu layer 1000b and Cr layer 1000c (Steps (g) to (o), FIGS. 8G-8O). Thus, address electrode 1000 is formed on the back side glass substrate 500.
The above-mentioned process using an etching solution is generally called "wet etching". In the conventional wet etching processes, the resist 2500 is formed from an organic material.
Further, in the conventional formation of electrodes by wet etching, a photolithographic step for forming a resist is indispensable.